1. Field of the Invention
This invention relates to a method of determining a choice made by a user, as indicated by the user's marking a response sheet, by analyzing the marks made on the response sheet.
2. Description of the Prior Art
Elections, academic tests, referendums, surveys, gambling schemes, and other endeavors often require the accurate counting, tabulation, or analysis of marks made on response sheets or ballot. Often, machines are used to perform this task, as manual counting is generally too slow and unreliable for most purposes. These machines are expected to provide the same, or better, accuracy than manual counting and to do so with increasing speed.
Response sheets are a form of a multiple-choice questionnaire. A user votes or selects a choice by making some sort of mark next to the name or choice printed on the sheet. Accurate counting of marked response sheets requires optically scanning the sheets, reliably detecting or reading every mark made on a response sheet and recognizing whether it is a valid vote or choice.
There are numerous different methods and apparatus pertaining to optically scanning documents, and detecting and recognizing marks on them. Most use some sort of pre-printed form and a scanning device that is adapted to the particular format of the form. For example, U.S. Pat. No. 4,813,708 describes a scanner for detecting timing marks and written marks on a response sheet that includes a read head that has tungsten lamps illuminating the sheet with infra-red light and phototransistors to sense infra-red light reflected from the surface of the sheet. A response sheet to be scanned or read is transported past the row of phototransistors and a lens focuses the image of the illuminated response sheet on to the phototransistors. The ink used for making the marks absorbs infra-red light. Therefore, when a phototransistor senses a significant drop of brightness in the infra-red light reflected from the response sheet, it is likely due to a passing mark. When the phototransistors sense less infra-red light, a mark indicating a valid choice is deemed to have been detected. The meaning of the choice is determined by the location of the mark on the response sheet and the choice is recorded.
Other systems have been designed that improve upon this system, such as that described in U.S. Pat. No. 5,248,872. Each of the prior art devices uses the reflection or absorption of light to determine the presence of a mark on a response sheet. Such systems have several shortcomings. First, the sheet must be filled out in an exact manner to register correctly. These systems do not register as choices marks that are commonly made to indicate such choices, such as check marks, and which marks are easily discernable as choices to human eyes.
Other disadvantages of these systems stem from the fact that a response area is treated as the smallest unit of the response sheet that is analyzed. Because the response area is not recorded and analyzed as a conglomeration of much smaller areas, no automated analysis is available for marginal or, partial markings in a response area.
Election Systems & Software, Inc. developed its Model 100 Precinct Counter with a Contact Image Sensor (CIS) as its reading technology. The CIS integrates a light source, lens, sensor, and video signal amplifier into a single module. It is essentially the same type of CCD or CMOS sensor that is used in fax machines and page scanners, which are well known in the art and is capable of reading the entire width of an 8.5″ wide response sheet. With this capability, the system was designed to employ readily available computer hardware and software to specify which segments of the sensor would be used to read the response sheet and to record, analyze and classify the generated data.
The employment of the CIS created a number of challenges regarding the accuracy, consistency, and the selection of marking devices employed in the system. Response sheets printed out of specifications, overly sensitive read heads, and smudged sensors created problems that lead to false readings. These problems lead to the development of a Model 100 system setup routine in which blank response sheets were fed into the machine and the sensitivity of the sensors was adjusted to eliminate false readings. This solution proved to be less than ideal, however, because the sensitivity of the sensors was occasionally too low to give an accurate reading of the response sheet. Also, the accuracy of the machines was often subject to the failings of the operator. Furthermore, inaccuracies were detected due to improper ballot printing and skewed feeding of sheets through the system.